The present invention relates to a copolyamide resin exhibiting excellent transparency. More particularly, the present invention relates to a transparent copolyamide resin which is produced by copolymerizing specific starting materials for polyamide, in specific proportions, and which has resistance to alcohols and resistance to boiling water together with high moldability.
The polyamide resin, owing to its well known excellence in such properties as rigidity, toughness, resistance to heat, and resistance to chemicals, has firmly established its fame as an engineering plastic. Among other species of polyamide resin, the transparent polyamide resin has been finding rapidly growing utility in a wide variety of applications in recent years because the transparent polyamide resin shows outstanding transparency and, at the same time, retains most of the highly desirable properties inherent in the polyamide resin.
The heretofore known varieties of transparent polaymide resin, however, suffer invariably from several drawbacks.
For example, the polyamide which comprises an alkyl-substituted hexamethylenediamine and isophatalic acid and/or terephthalic acid and the polyamide which, as disclosed in U.S. Pat. No. 4,264,762, comprises bis(3-methyl-4-aminocyclohexyl)methane and isophthalic acid and lactam exhibits poor in resistance to methanol and ethanol.
The polyamide which comprises bis(4-aminocyclohexyl)methane and isophthalic acid and the polyamide which, as disclosed in U.S. Pat. No. 3,597,400, comprises bis(4-aminocyclohexyl)methane, hexamethylenediamine, terephthalic acid, and isophthalic acid, possesses high melt viscosity, but exhibits very poor moldability.
The polyamide which comprises hexamethylenediamine and isohthalic acid and/or terephthalic acid blushes when it is treated in boiling water.
As described above, none of the transparent polyamides so far developed shows sufficient resistance to alcohols, resistance to boiling water, and retains high moldability altogether.
The present inventors, in appreciation of the true state of affairs described above, have continued a study in search of a transparent polyamide resin which shows resistance to alcohols, resistance to boiling water, and retains high moldability. As the result of their study, the present inventors have found that a transparent copolyamide which comprises constitutional units derived from a diamine component comprising (a) bis(3-methyl-4-aminocyclohexyl)methane and (b) hexamethylenediamine and a dicarboxylic acid component comprising (c) isophthalic acid and (d) terephthalic acid, the molar ratio of the aforementioned components simultaneously satisfying the following two formulas: EQU (a):(b)=3:97 to 18:82 EQU (c):(d)=60:40 to 90:10
and relative viscosity n.sub.rel (eta) of the copoloyamide being 1.9 to 2.5 as measured at 25.degree. C. and a concentration of 1 g/dl in 98% concentrated sulfuric acid, can satisfy, at the same time, all of the requirements mentioned above.